Electronic toll collection systems conduct toll transactions electronically using RF communications between a vehicle-mounted transponder (a “tag”) and a stationary toll plaza transceiver (a “reader”). A reader is sometimes referred to as a roadside unit (RSU) and a tag is sometimes referred to as an on-board unit (OBU). An example of an electronic toll collection system is described in U.S. Pat. No. 6,661,352 issued Dec. 9, 2003 to Tiernay et al., and owned in common with the present application. The contents of U.S. Pat. No. 6,661,352 are hereby incorporated by reference.
In a typical electronic toll collection system, the reader broadcasts a wakeup or trigger RF signal. A tag on a vehicle passing through the broadcast area or zone detects the wakeup or trigger signal and responds with its own RF signal. There are generally two types of tags: active transponders that generate and send their own signal and backscatter transponders that modulate a continuous wave signal provided by the reader. In either case, the tag responds by sending a response signal containing information stored in memory in the transponder, such as the transponder ID number, the last toll plaza ID number, etc. The reader receives the response signal and conducts an electronic toll transaction, such as by debiting a user account associated with the transponder ID number. The reader may then broadcast a programming RF signal to the tag. The programming signal provides the tag with updated information for storage in its memory. It may, for example, provide the tag with a new account balance and/or a new toll plaza ID number.
Some existing electronic toll collection systems feature relatively simple on-board units (tags) that have no sensory indicators, such as lights, display screens, speakers, or other sensory devices. Accordingly, a vehicle occupant cannot know whether or not his or her on-board unit is functioning correctly. In particular, as the vehicle passes through a toll collection plaza or zone the vehicle occupant may receive no indication as to whether a toll transaction has taken place.
It would be advantageous to provide for a device that may be used in conjunction with existing electronic toll collection system tags to signal occurrence of an electronic toll communication.